Electric discharge device system



y 1935. G.{ZW. GARMAN 2,001,530

ELECTRIC DISCHARGE DEVICE SYSTEM Filed March 20, 1930 ITWVefitcT:

G eorgeW Garman idm PMs-Attorney.

Patented May 14, 1935 UNITED-STAT ELECTRIC DISCHARGE DEVICE SYSTEM IGeorge W. Garman, Scotia, N. Y., assignor to General Electric Company,

. New York a corporation of Application March 20, 1930, Serial No.437,627

' 6 Claims. (01. 250-27) My invention relates to means for controllingthe starting of current through electric discharge devices, wherein thetransmission of current is effected both by electrons and by positiveions,

and has for its principal object the provision of animproved arrangementand method of operation for controlling or varying the times at whichcurrent starts through such a. device.

It is well known that the starting of current through a device includinga cathode and anode immersed in a rarefied gas or vapor, such as mercuryvapor at a pressure of a few microns, may be controlled by a grid andthat such a grid is ineffective to interrupt the current after it isestablished. If an alternating potential is applied between the cathodeand anode of the device, control by the grid is regained at the end ofeach half cycle. If a unidirectional potential is applied between thecathode and anode, some means must be provided for temporarilyneutralizing the efiect of this potential.

It has been proposed to control the instant of current starting by meansof an alternating grid potential of the same frequency as that of theanode potential, the instant of starting in the half cycle ofv anodevoltage being determined either by shifting the phase of the alternatinggrid potential or by varying the magnitude of a unidirectional grid biaspotential. These methods of, control, however, are not altogetherSatisfactory for the reason that they involve the provision of phaseshifting devices or more or lesscomplicated apparatus. In accordancewith my invention, this difiiculty is largelygavoided by the provisionof an improved and simplified means for controlling or regulating thegrid potential of the device.

My invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawing, and itsscope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 illustrates an arrangement wherein myinvention has been embodied; and Figs. 2and- 3 are a group of curveswhich are copies of oscillograms made during the operation of theapparatus.

The apparatus includes an electric discharge device I0 through whichcurrent is supplied from an alternating current circuit I I to a directcurrent load I2. Since the device I0 conducts current only in onedirection, only current impulses corresponding to alternate half. cyclesare supplied to the load I2. It will be evident, however, that myinvention is applicable to apparatus operable to rectify both halfcycles of the alternating potential applied to theanode circuit orcircuits of the electric discharge apparatus.

In either case, the part of the half cycle during which current istransmitted to the direct current load is determined by the gridpotential or potentials of the electric discharge apparatus.

Thus in the illustrated embodiment of the apparatus, current is suppliedto the load I2 during a part of the half cycle determined by thepotential of the grid I3.

The grid potential control means of the device I 0 "includesa spacedischarge device I4 and a transformer I5. As indicated by Fig. l of thedrawing, a transformer I6.connected to the circuit I I is provided withthree secondary windmgs one of which is arranged to apply an alternatingcurrent to the plate circuit of the device I 4 and the other two 'ofwhich supply heating current respectively to the cathode of the deviceI4 and the device III. A direct current potential source I1 andariiimpedance element or resistor I8 are connected in parallelwith oneanother in the grid or input circuit of I the device I4. The output oranode circuit of this device includes a secondary winding I9 of thetransformer I6 and the primary windingzfl of the transformer I5, animpedance element such as a resistor 2| being connected in shunt to thewinding .20. i The operation of the above described apparatus will bebetter understood by reference to Figs. 2 and 3 of the accompanyingdrawing. Referring more particularly to Fig. 2, the curve Ea representsone. cycle of alternating potential applied to'the'anode 23 of thedevice I0 and also to the circuit including the device I 4 and theprimary winding ofthe grid transformer I5. The curve Ib represents thecurrent flowing in this latter circuit; It will be noticed that duringthe negative half cycle of potential Ea this curve follows substantiallya Sine wave with its zero axisand phase displaced. At the end of thefirst half cycle, however, the potential applied to the primary windingof the. transformer I5 is interrupted due to the unilateral conductivitycharacteristics of the device I4. However, the. primary winding 20 isshunted by a resistor 2| and the energy storedin the magnetic field ofthe transformer I5 is gradually dissipated 'in this resistor the currentfollowing the curve I]: as illustrated in the figure. Grid transformer.I5 is loaded for only a fraction of a cycle and has the characteristicsof areactor. The counter-electromotive force of the transformer I5 dueto the current Ib, is represented by the curve Eb, which it is seen, isconsiderably distorted from a Sine wave. The curve E0 represents thegrid con-' trol characteristic of the. valve I 0; that is, the gridpotential of the device I0 must be made less negative for any givenvalue of anode potential represented byxthe curve Ea than thecorresponding valueof the curve Ec in order for the valve Into conductcurrent. It willbe noted that the curve Eb intersects the 'curve'Ec'atthe point X so that the valve II] will become conductive at this pointin the half cycles of positive anode potential to pass load current tothe device 12.

curve E atthe point Y aliiw'hlchzpolnt the device I0 is made conductiveto pass current to load device l2. Thus, it is seenthatby varying thegrid potential of the device 14', the distorted potential produced byconnecting an electric valve in series with the primary winding oi thegrid transformer is varied in magnitude to intersect the critical gridpotential curve at any desired point and thus render thedevice I.conductive for any desired portion of its respective positive haltcycles of anode potential.

In Fig. 3, the anode voltage of .the device i0 is indicated by thecurveEa, the anode current is indicated by the curve Is, and thepotential applied to the grid or the device II is indicated by the.CUYVBIEgJ ltiwfll hfl noted that littb or no current is transmitted tothe direct current load circuit when acommratively low negative voltageis applied .to the'grid of the device M and that the direct current ofthe load increases as the magnitude of this negative potential isincreased.

Variation of the potential E; is efiected by ad-. justmentof theresistor. Thus when the.ad justable terminalfl is inits ilhmtratedposition. a comparatively "large negative potential :ls'appliedto theinput circuit of1the .dev'lce H, the plate impedance of this; device isincreased, the alternating potential applied to-the. grid I3 iscomparatively low, andmaximum current flows through the device ill-forthe reason that the negative potential oi. the grid 13 is decreased atthe time that the -.corresponding anode 13 is positive.

If the negative-gridpotcntial'of the dew-ice M be gradually decreased inmagnitude, the magnitude and wave shape of the alternatina Potentia-lapplied to the grid; l3 through the transtormer I5 is changed .and'agradual decrease in the current of the direct current load is producedas indicated by the curve Ill Of Fig. 3.

The change in grid bias potential of. thedevice M required to vary thedirect garment-o! the load 12 from its minimum to its maximmn value canreadily be varied by change in there-- sistance o! the resistor 21,change in the ampliflcation ratio or. the device ,or change in theinductance oi the tramtormor l5. What I claim as new and desire tosecure by Letters Patent of the United States is:

1. The combination of a vapor electric discharge device provided with agrid for controlling the starting of current between its cathodeandanode, means for applying an alternating potential to said grid, aspaoe discharge device arranged to vary the character of said potential,

and means 'forccntrolling the current in said space discharge deviceincluding a. potential source and a resistor connected in parallel withone another in :the'input circuit of said space discharge device. I

2.The combination of a circuit nicluding a vapor electric dischargedevice provided with a grid for controlling the-current 01' saidcircuit, means including atranstormer interposed hevalues. 7

tween said circuit and said grid for controlling the potential of saidgrid, a source of alternating current, a space discharge deviceconnected in series with said sourceof alternating current and-a windingof said transformer'to supply unidirectional current impulses thereto,and means 'for varying the impedance of said space discharge device,whereby the magnitude of the current in said circuitis varied. betweendifferent 3. The combination of a vapor electric discharge deviceprovided with a grid for controlling the starting 0'! current betweenits cathode and anode, a source of alternating potential, a

transformer having one winding interposed between sald cathode and saidgrid, rectifying means included in circuit with the other winding ofsaid transformenand said source of alternating potential for suppressinghalf cycles of said supply potential of predeternuned polarity from saidgrid, impedance means connected in parallelcto lsaid transformer toprovide a path for inductive and means for varying the e'nerglzation orsaid transformer to control the current carried by said dischargedevice. r

.4. The combination of a vapor electricdischarge device provided wlthagrid for controlling the starting of current between'lts cathode andanode, a circuit for app y n an alternating potential to said gridincluding asource oi alterhating current, and a space discharge devicecormected in scrim with one winding of a transformer, the othertransformer winding being connected to said grid, and means for varyingthe impedance of said space discharge device variably to distort thewave form of said alterhating potential.

5. The combination or a vapor discharge device including an anode, acathode and agrid for controlling the starting a: current'between thecathode and anode, a grid circuit for said device, a space dischargedevice including a cathode, an anode and a grid, an output circuittherefor including an electromagnetic energy storage elementcouplod tosaid grid circuit, a transient by pass circuit connected across saidenergy storage element, a source of alternating potential for sup-:plying anode potential to said space discharge device, and means forselectively varying the,

impedance of said space discharge device to control the magnitude andwave form of the energy supplied by said electromagnetic storage elementto the gridclrcuit of saidvapor dis-I 6. The combination of a vapordischarge device including an anode, a cathode :and a grid forcontrolling the starting of current between said cathode and said anode,an electromagnetic energy storage element, a space discharge devicehaving an anode circuit coupled to the grid ctrcult or said vapordischarge device through said energy storage element, a source ofalternating potential for the anodes of both said devices, and means forselectively varying the impedanceuof said space discharge device tocontrol the magnitude and waveform of the energysupplled by said energystorage element to said grid o'fsaid vapor discharge device whereby saidlatter device is rendered conductive for any selected portion of thepositive hall cycles of anode potential.

GEORGE woman.

